The automotive industry has turned to the use of interior trim components such as door panels comprising a polyvinyl chloride shell. See, for example, the trim components disclosed in U.S. Pat. No. 3,123,403. The acceptance of such components has been because inter alia this type of construction permits a wide latitude in styling and color, and grain effects which are most desired particularly in the interior design of automobiles.
The current state of the art includes methods to form preformed grained vinyl shells from dry thermoplastic powder particles which are applied to a heated shell mold from a powder box to form a one piece shell whose shape will correspond to that of the mold casting surface. Examples of such methods and apparatus are set forth in U.S. Pat. No. 3,492,307 issued Jan. 27, 1970, and U.S. Pat. No. 4,623,503 issued Nov. 18, 1986. Other devices for heating are set forth in U.S. Pat. Nos. 489,299 issued Jan. 3, 1893; 1,763,290 issued Feb. 22, 1916; 2,288,012 issued June 30, 1942; 2,869,630 issued Jan. 20, 1959; and 3,372,820 issued Mar. 12, 1968.
None of the aforesaid methods and apparatus for manufacture or resultant manufacture is directed to a process or apparatus which includes a rotational tube sheet operative to heat a multitude of mold shapes in an energy efficient manner so as to form single piece shells from heat fusable thermoplastic material of differing shape such as interior panel components of an automobile.